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18. January 2015

More than aluminum

More than aluminum

Editor's choice: Eric Roegner – pictured below, chief operating officer for Alcoa investment castings, forgings, and extrusions – explains the company’s aerospace solutions role.

Alcoa does a lot more than supply aluminum. The company also is a global leader in lightweight materials engineering and manufacturing. It holds key market positions in aerospace sheet and plate produced by its midstream business, Global Rolled Products (GRP). Its downstream business, Engineered Products and Solutions (EPS), produces aerospace forgings, extrusions, investment castings, and fastening systems. In 2013, these two value-add businesses – GRP and EPS – accounted for 57% of Alcoa’s total revenues.

Alcoa’s downstream component is composed of businesses heavily weighted toward aerospace. Unlike the sheet and plate business, most of the downstream businesses will both design and qualify parts such as fasteners or investment castings, where the company will work closely with a customer to optimize form, fit, and function. This working relationship can also extend to other partners in the supply chain, from Tier 1 to small shops.

Eric Roegner, chief operating officer for Alcoa investment castings, forgings and extrusions, oversees the investment castings business, formerly known as Howmet, based in Whitehall, Mich. “That business makes investment castings – the vast majority of which are nickel super-alloys that go into jet engine turbines – as well as titanium castings and rotating parts,” Roegner says.

Additionally, a structural castings business – located in Whitehall and other locations globally – deals partly with aluminum, but mostly with titanium and some nickel. The structural castings business uses aluminum for complicated structures around nozzles and ducting. Components closer to an engine’s hot section can be made of titanium or nickel.

Roegner, who also is president of Alcoa Defense, oversees the company’s Cleveland-based forgings business, which he describes as “basically everything that holds an airplane together that you don’t see, including the landing gear, wheels, and brakes.”

Roegner says people think of Alcoa and aerospace as “a lot of aluminum,” but he explains that about 60% of that segment has no aluminum in it at all. About one third, the fastening systems group, is mainly titanium, steels, and nickel alloys.

“We not only sell fasteners but the whole installation system. For the incredibly tight requirements you need for torque, access, plus the speed of assembly lines in aerospace, we’ll sell the whole system for the fasteners as well as the tooling and the equipment used to install them,” Roegner explains. “We also have vendor-managed inventory systems where we’ll stock the bins, too.”

Roegner proudly relates the group invented the fasteners that manage the lightning-strike protection on carbon-fiber aircraft, such as the Boeing 787 and Airbus A350. If an aircraft’s plastic skin gets hit, the fasteners mitigate the electrons associated with the lightning. At the same time, the fasteners manage all the requirements of joining a carbon fiber skin to a metallic or other carbon fiber structure, including differential thermal expansion and preventing galvanic corrosion. “And the fasteners are able to do this for 30 years,” Roegner adds.

Another third of the aerospace business is investment castings – the airfoils for jet engines – particularly in the hot section.

Roegner notes that Alcoa is a leader in super-alloy technology, not only in the metallurgy to make single-crystal, directionally solidified equiaxed airfoils for the high-pressure and low-pressure turbine sections, but also parts in the compressor section and the structure surrounding the rotating parts in the engine.

For single-crystal blades, Roegner says, “We can provide advanced grain orientation control in terms of both position and tolerance for the incredibly loaded portions of the engine. In addition, we produce three-dimensional, multi-wall cores and cast these into airfoils to manage the airflow with air going at different rates into different parts of the component to actively manage the cooling.”

Alcoa also offers coating technologies for blades and vanes: chemical vapor deposition and electron beam plasma vapor deposition. “We produce airfolis that operate in an environment at temperatures in excess of 3,000°F, well above the melting temperature of the metal.”

That technology is used on the most advanced engines in the world: GE’s GEnX, CFM International’s LEAP, Rolls-Royce’s Trent XWB, and Pratt & Whitney’s Geared Turbofan and F-135.

“When an engine OEM is designing a new engine and needs to push the performance envelope, the very first call that is made is to get our engineers and their engineers together to figure out what is physically possible, and we give them the envelope within which they can design the most advanced engines in the world,” Roegner says.

The final third of the business addresses the structure, predominantly the airframe, and encompasses sheet, plate, forgings, extrusions, and structural castings. These go into the built-up structures in aircraft, such as stiffened panels for the wings or fuselage. But the forgings business is not all aluminum. In the Lockheed Martin F-35 Joint Strike Fighter, for example, the big bulkheads and wing spars are forged in either titanium or aluminum.

Roegner stresses that the company is not content with merely making simple shapes: “We aim where you have to push the envelope on whatever the product form is.”
 
A rich history of R&D

Alcoa’s connection with aerospace dates back to the Wright Brothers and their first Flyer.

“The reason that plane could fly is that Alcoa invented an aluminum alloy they could use in the casting of their engine’s crank case, and we have been integral to aerospace ever since,” Roegner says.

“More than 90% of all of the aluminum alloys and tempers flying in the air today were developed by the Alcoa technology center just north of Pittsburgh.”

It is one of the largest light metals research facilities in the world, with more than 600 researchers, including more than 120 Ph.Ds. Research there also includes alloy and temper development, corrosion, coatings, bonding, and joining.

Another development center, in Whitehall, Mich., conducts titanium and nickel research.

“In the history of jet engines, the advances, particularly in nickel super-alloys and advanced casting structures, being able to make thinner trailing edges, more advanced cooling patterns, cooling the base of the blades – those were all developed at that research center,” Roegner notes.

A third research center in Carson, Calif., develops joining systems for the fasteners business.
 
Partnering for success

When an OEM is developing an airplane wing and the fasteners and the metal structure inside, teams of Alcoa engineers will sit down with the OEM engineers and hash out operating envelopes. They will define what is physically possible, whether the material is carbon fiber or metallic, and what will optimize that structure.

Similarly, Roegner says Alcoa can have the same kind of discussions with Tier 1s, such as Spirit Aerosystems or the Japanese companies Mitsubishi Heavy Industries Ltd., IHI Corp., and Kawasaki Heavy Industries Ltd.

“Whether it’s titanium or aluminum forgings, the industry really wants to simplify the supply chain, and consequently, very rarely will you see a bid for just a forging anymore,” Roegner explains. “What they want is a bid for a finished, machined part.”

Alcoa can provide the desired properties in a forging – either with its own capabilities or by working with a partner – and can create forgings in a way that links with how a partner machines that part to minimize distortion. Take, for example, the F-35. One of its bulkheads is about 20ft long, 6ft tall, and more than a foot thick, and post-machining, it has less than a tenth of an inch distortion tip-to-tip.

“That’s coming out of our processes,” Roegner says. “There are some things we’ll do entirely on our own, and there are others where we’re going to hand-pick a different partner, either for a type of material or geometry to leverage their expertise.”

What can be the best answer for the customer may leverage the capabilities resident in the industry.

“Ultimately, we want to get the best technology into the hands of the OEMs and at the price point that helps them meet not only the performance mission, but also the affordability mission,” Roegner states.

The partners Alcoa chooses depend on the particular product form. Rarely does any machine shop offer everything under one roof, Roegner notes. He describes the industry as a “great, big conglomerate of ‘coopetition’ where someone wins the lead and outsources bits and pieces to others.”

Alcoa Engineered Structures manages the supply chain of make-versus-buy decisions and then coordinates with its partners.

“Whether we’re selling a big titanium casting to Triumph for the Boeing C-17, or a big bulkhead, or even a pylon, we will optimize that network so that we bring the best to bear.”

The process could involve doing in-house or outsourced machining, or it could be some of the coating steps. Alcoa also may be brought in as a partner, for HIPing (hot isostatic pressing) used in stress-relieving in high-temperature alloys such as nickel, or for revert-processing titanium into ingots.

“You can have some very interesting but very pragmatic partnerships that form throughout the supply chain,” Roegner says.
 
Additive manufacturing, too

Alcoa has been using non-traditional technologies such as additive manufacturing in its casting business for more than 15 years. Roegner points out that investment casting was one of the first industries to really capitalize on additive manufacturing, using it to make prototype parts and sacrificial patterns.

For investment castings for low-volume, complicated parts, Roegner says printing patterns “saves a huge amount of money on tooling, and it also saves a huge amount of time.” He adds, “It allows you to quickly make design changes and see what works and what doesn’t work on the pattern.”

The company also is looking to use additive manufacturing to print tooling (fixtures) and cores, and it is looking at the process of using metals – both powder-bed and wire-fed – on nickel, titanium, steels, and aluminums to print actual parts.

Roegner notes the process still has limitations. “You have to be able to resist cracks, and you need the fatigue resistance.”

He adds the industry has to figure out if it can get those properties, either without a wrought step that comes with sheet-plate forging or without the advanced single-crystal structures that the additive process can’t duplicate.

“If it is a simple, straightforward, equiaxed, non-loaded, non-fatigue-sensitive part, I think eventually some lower-volume production parts will be made through additive manufacturing,” Roegner relates.

Roegner says that given time, additive technologies are going to be used more frequently for more steps of the manufacturing process. “Simple, small, non-load-bearing nozzle structures inside of engines, that’s probably at some point going to go additive. But if you’re looking at the rotating parts – the blades and the big discs that need load-bearing and high-temperature resistance – I think additive manufacturing may be helpful at different stages in the process, especially prototyping early in product development. But until engineers crack the code on some fundamental physics, I think the standard investment castings process is not only going to be safe, but we’ve got a lot of growth ahead of us in the next couple of decades.”
 
www.alcoa.com

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